Internal combustion engines chemically convert the energy stored in fuel by combustion into kinetic energy by moving up and down pistons accommodated on a crankshaft by means of connecting rods in a reciprocating piston internal combustion engine according to a two or four cycle principle while rotating the crankshaft and cylinders. Particularly in motor vehicles, internal combustion engines must have a wide performance range to meet the performance requirements of different modes such as city driving, interurban driving and highway driving. Most internal combustion engines are therefore over-dimensioned for the average performance requirements and are thus operated at lower efficiency, resulting in an elevated demand for fuel. To increase efficiency within the partial load range, it is proposed to shut off individual cylinders of the internal combustion engine, that is, not to fire them by not supplying fuel to the cylinders and opening the valves to control the exchange of gas. In such embodiments, the connecting rods and pistons for the shut-off cylinders need to continue operating under a corresponding expenditure of energy to further improve the efficiency of such internal combustion engines.
To further improve efficiency, a reciprocating piston internal combustion engine disclosed in DE 31 45 381 A1 is divided into two subunits which each containing a part of the working cylinders of the internal combustion engine, the connecting rods and pistons of which are connected to a crankshaft part. The crankshaft parts of the two subunits can be coupled to each other by means of a clutch, so that both subunits can be combined under a full load when the clutch is engaged, and a subunit can be decoupled in the partial load range by disengaging the clutch. The decoupling occurs by axially shilling the decouplable subunit, wherein its crankshaft part and the connecting rods on the crankshaft cranks must be accommodated in axial floating bearings. The crankshaft must be precisely positioned in relation to the housing of the internal combustion engine, and the connecting rods on the crankshaft must be precisely positioned in relation to the pistons operating in the housing. The two subunits of the internal combustion engine are turned on and off by means of a device for axially shifting that must be operated with additional energy under a full load, which in turn reduces the efficiency of the internal combustion engine.